Surfactants are well known materials which can be generally described as having a hydrophobic moiety and a hydrophilic group per molecule. A wide variety of these materials are known and are classified as anionic, cationic, nonionic and amphoteric. They are well known to have numerous uses such as emulsifiers, detergents, dispersants and solubilizing agents in the field of cosmetics, textile treatment, industrial and personal cleaning preparations, corrosion inhibitors and the like.
Anionic surfactants carry a negative charge on the hydrophilic portion, usually in the form of a carboxylate, phosphate, sulfate or sulfonate. These surfactants find use in emulsion polymerization as well as in agricultural chemicals, personal care and household products, industrial and institutional cleaners. They function as emulsifiers, cleaners, wetting agents, foaming and frothing agents such as for shampoos, car washes, carpet shampoos, hand dish washing, latex foaming, oil recovery and other industrial uses.
Surfactants generally are compounds having one hydrophilic group and one hydrophobic moiety. Recently, a group of compounds having two hydrophobic moieties and two hydrophilic groups have been introduced. These have become known as "gemini surfactants" in the literature (Chemtech, March 1993, pp 30-33), and J. American Chemical Soc., 115, 10083-10090, (1993) and the references cited therein. Since their introduction, cationic and anionic "gemini surfactants" have been disclosed. Other surfactant compounds having two hydrophilic groups and two hydrophobic moieties have been disclosed but not referred to as gemini surfactants.
Sulfate, phosphate, and carboxylate surfactants are currently disclosed in the literature (See JAOCS 67, 459 (1990); JAOCS 68, 268 (1991); JAOCS 68, 539 (1991); and JAOCS 69, 626 (1992). In each case, a secondary hydroxyl is sulfated, carboxylated, or phosphated.
Secondary hydroxyl's phosphate poorly in that phosphoric anhydride leads to olefin production (dehydration) while polyphosphoric acid results in high levels of phosphoric acid and unphosphated material. The present invention results in compounds which are characterized by primary hydroxyl groups which can more efficiently be functionalized.
Similarly, sulfation can also lead to dehydration by-products. Carboxymethylation of secondary hydroxyl groups is also difficult resulting in low yields.
One author [JACS 115, 10,083 (1993) and JACS 113, 1451 (1991)] prepares a phosphate on a primary hydroxyl group. But in these references, it is necessary to utilize mixed alcohols to incorporate a hydrophobe into the molecule. This leads to the production of mixed diphosphate, a necessary outgrowth of using the mixed alcohols. This difficulty is eliminated in the present invention. In addition, high monoalkylphosphates as well as diphosphates can be prepared according to the present invention.
Due to the need for new and more effective and efficient surfactants, as well as the need for mild surfactants which are biologically compatible in an ecologically sensitive environment as well as the need for more effective and efficient surfactants, effort has been made to develop a new class of compounds, which demonstrate improved surface-active properties that are further characterized as mild, and environmentally benign.